Internet Engineering Task Force H. Chen, Ed.
Internet-Draft Huawei Technologies
Intended status: Experimental R. Torvi, Ed.
Expires: September 19, 2018 Juniper Networks
March 18, 2018
Extensions to RSVP-TE for LSP Ingress FRR Protection
draft-ietf-teas-rsvp-ingress-protection-17.txt
Abstract
This document describes extensions to Resource Reservation Protocol -
Traffic Engineering (RSVP-TE) for locally protecting the ingress node
of a Point-to-Point (P2P) or Point-to-Multipoint (P2MP) Traffic
Engineered (TE) Label Switched Path (LSP). It extends the fast-
reroute (FRR) protection for transit nodes of an LSP to the ingress
node of the LSP. The procedures described in this document are
experimental.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 19, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Ingress Local Protection Example . . . . . . . . . . . . . 4
1.2. Ingress Local Protection Overview . . . . . . . . . . . . 5
2. Ingress Failure Detection . . . . . . . . . . . . . . . . . . 6
2.1. Source Detects Failure . . . . . . . . . . . . . . . . . . 6
2.2. Backup and Source Detect Failure . . . . . . . . . . . . . 7
3. Backup Forwarding State . . . . . . . . . . . . . . . . . . . 7
3.1. Forwarding State for Backup LSP . . . . . . . . . . . . . 8
4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 8
4.1. INGRESS_PROTECTION Object . . . . . . . . . . . . . . . . 8
4.1.1. Class Number and Class Type . . . . . . . . . . . . . 9
4.1.2. Object Format . . . . . . . . . . . . . . . . . . . . 9
4.1.3. Subobject: Backup Ingress IPv4 Address . . . . . . . . 10
4.1.4. Subobject: Backup Ingress IPv6 Address . . . . . . . . 11
4.1.5. Subobject: Ingress IPv4 Address . . . . . . . . . . . 11
4.1.6. Subobject: Ingress IPv6 Address . . . . . . . . . . . 12
4.1.7. Subobject: Traffic Descriptor . . . . . . . . . . . . 12
4.1.8. Subobject: Label-Routes . . . . . . . . . . . . . . . 13
5. Behavior of Ingress Protection . . . . . . . . . . . . . . . . 13
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1.1. Relay-Message Method . . . . . . . . . . . . . . . . . 13
5.1.2. Proxy-Ingress Method . . . . . . . . . . . . . . . . . 14
5.2. Ingress Behavior . . . . . . . . . . . . . . . . . . . . . 15
5.2.1. Relay-Message Method . . . . . . . . . . . . . . . . . 16
5.2.2. Proxy-Ingress Method . . . . . . . . . . . . . . . . . 16
5.3. Backup Ingress Behavior . . . . . . . . . . . . . . . . . 18
5.3.1. Backup Ingress Behavior in Off-path Case . . . . . . . 18
5.3.2. Backup Ingress Behavior in On-path Case . . . . . . . 20
5.3.3. Failure Detection and Refresh PATH Messages . . . . . 21
5.4. Revertive Behavior . . . . . . . . . . . . . . . . . . . . 21
5.4.1. Revert to Primary Ingress . . . . . . . . . . . . . . 22
5.4.2. Global Repair by Backup Ingress . . . . . . . . . . . 22
6. Security Considerations . . . . . . . . . . . . . . . . . . . 22
7. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 22
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
9. Co-authors and Contributors . . . . . . . . . . . . . . . . . 23
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 25
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
11.1. Normative References . . . . . . . . . . . . . . . . . . . 25
11.2. Informative References . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
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1. Introduction
For a MPLS TE LSP, protecting the failures of its transit nodes using
fast-reroute (FRR) is covered in RFC 4090 for P2P LSP and RFC 4875
for P2MP LSP. However, protecting the failure of its ingress node
using FRR is not covered in either RFC 4090 or RFC 4875. The MPLS
Transport Profile (MPLS-TP) Linear Protection described in RFC 6378
can provide a protection against the failure of any transit node of a
LSP between the ingress node and the egress node of the LSP, but
cannot protect against the failure of the ingress node.
To protect against the failure of the (primary) ingress node of a
primary end to end P2MP (or P2P) TE LSP, a typical existing solution
is to set up a secondary backup end to end P2MP (or P2P) TE LSP. The
backup LSP is from a backup ingress node to backup egress nodes (or
node). The backup ingress node is different from the primary ingress
node. The backup egress nodes (or node) are (or is) different from
the primary egress nodes (or node) of the primary LSP. For a P2MP TE
LSP, on each of the primary (and backup) egress nodes, a P2P LSP is
created from the egress node to its primary (backup) ingress node and
configured with BFD. This is used to detect the failure of the
primary (backup) ingress node for the receiver to switch to the
backup (or primary) egress node to receive the traffic after the
primary (or backup) ingress node fails when both the primary LSP and
the secondary LSP carry the traffic. In addition, FRR may be used to
provide protections against the failures of the transit nodes and the
links of the primary and secondary end to end TE LSPs.
There are a number of issues in this solution:
o It consumes lots of network resources. Double states need to be
maintained in the network since two end to end TE LSPs are
created. Double link bandwidth is reserved and used when both the
primary and the secondary end to end TE LSPs carry the traffic at
the same time.
o More operations are needed, which include the configuration of two
end to end TE LSPs and BFDs from each of the egress nodes to its
corresponding ingress node.
o The detection of the failure of the ingress node may not be
reliable. Any failure on the path of the BFD from an egress node
to an ingress node may cause the BFD to indicate the failure of
the ingress node.
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o The speed of protection against the failure of the ingress node
may be slow.
This specification defines a simple extension to RSVP-TE for local
protection (FRR) of the ingress node of a P2MP or P2P LSP to resolve
these issues. Ingress local protection and ingress FRR protection
will be used exchangeably.
Note that this document is experimental. Two different approaches
are proposed to transfer the information for ingress protection.
They both use the same new INGRESS_PROTECTION object, which is sent
in both PATH and RESV messages between a primary ingress and a backup
ingress. One approach is Relay-Message Method (refer to section
5.1.1 and 5.2.1), the other is Proxy-Ingress Method (refer to section
5.1.2 and 5.2.2). Each of them has its advantages and disadvantages.
It is hard to decide which one is used as a standard approach now.
It is expected that the experiment on the ingress local protection
with these two approaches provides quantities to help choose one.
The quantities include the numbers on control traffic, states, codes
and operations. After one approach is selected, the document will be
revised to reflect that selection and any other items learned from
the experiment. The revised document is expected to be submitted for
publication on the standards track.
1.1. Ingress Local Protection Example
Figure 1 shows an example of using a backup P2MP LSP to locally
protect the ingress of a primary P2MP LSP, which is from ingress Ia
to three egresses: L1, L2 and L3. The backup LSP is from backup
ingress Ib to the next hops R2 and R4 of ingress Ia.
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******* ******* S Source
[R2]-----[R3]-----[L1] Ix Ingress
*/ & Rx Transit
*/ & Lx Egress
*/ & *** Primary LSP
*/ & &&& Backup LSP across
*/ & logical hop
*/ &
*/ ******** ******** *******
[S]---[Ia]--------[R4]------[R5]-----[L2]
\ | & & *\
\ | & & *\
\ | & & *\
\ | & & *\
\ | & & *\
\ |& & *\
[Ib]&&& [L3]
Figure 1: Ingress Local Protection
In normal operations, source S sends the traffic to primary ingress
Ia. Ia imports the traffic into the primary LSP.
When source S detects the failure of Ia, it switches the traffic to
backup ingress Ib, which imports the traffic from S into the backup
LSP to Ia's next hops R2 and R4, where the traffic is merged into the
primary LSP, and then sent to egresses L1, L2 and L3.
Note that the backup ingress is one logical hop away from the
ingress. A logical hop is a direct link or a tunnel such as a GRE
tunnel, over which RSVP-TE messages may be exchanged.
1.2. Ingress Local Protection Overview
There are four parts in ingress local protection:
o Setting up the necessary backup LSP forwarding state based on the
information received for ingress local protection;
o Detecting the primary ingress failure and providing the fast
repair (as discussed in Sections 2 and 3);
o Maintaining the RSVP-TE control plane state until a global repair
is done; and
o Performing the global repair(see Section 5.4.2).
The primary ingress of a primary LSP sends the backup ingress the
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information for ingress protection in a PATH message with a new
INGRESS_PROTECTION object. The backup ingress sets up the backup
LSP(s) and forwarding state after receiving the necessary information
for ingress protection. And then it sends the primary ingress the
status of ingress protection in a RESV message with a new
INGRESS_PROTECTION object.
When the primary ingress fails, the backup ingress sends or refreshes
the next hops of the primary ingress the PATH messages without any
INGRESS_PROTECTION object after verifying the failure. Thus the
RSVP-TE control plane state of the primary LSP is maintained.
2. Ingress Failure Detection
Exactly how to detect the failure of the ingress is out of scope.
However, it is necessary to discuss different modes for detecting the
failure because they determine what is the required behavior for the
source and backup ingress.
2.1. Source Detects Failure
Source Detects Failure or Source-Detect for short means that the
source is responsible for fast detecting the failure of the primary
ingress of an LSP. Fast detecting the failure means detecting the
failure in a few or tens of milliseconds. The backup ingress is
ready to import the traffic from the source into the backup LSP(s)
after the backup LSP(s) is up.
In normal operations, the source sends the traffic to the primary
ingress. When the source detects the failure of the primary ingress,
it switches the traffic to the backup ingress, which delivers the
traffic to the next hops of the primary ingress through the backup
LSP(s), where the traffic is merged into the primary LSP.
For an LSP, after the primary ingress fails, the backup ingress MUST
use a method to verify the failure of the primary ingress before the
PATH message for the LSP expires at the next hop of the primary
ingress. After verifying the failure, the backup ingress sends/
refreshes the PATH message to the next hop through the backup LSP as
needed. The method may verify the failure of the primary ingress
slowly such as in seconds.
After the primary ingress fails, it will not be reachable after
routing convergence. Thus checking whether the primary ingress
(address) is reachable is a possible method.
When the previously failed primary ingress of a primary LSP becomes
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available again and the primary LSP has recovered from its primary
ingress, the source may switch the traffic to the primary ingress
from the backup ingress. A operator may control the traffic switch
through using a command on the source node after seeing that the
primary LSP has recovered.
2.2. Backup and Source Detect Failure
Backup and Source Detect Failure or Backup-Source-Detect for short
means that both the backup ingress and the source are concurrently
responsible for fast detecting the failure of the primary ingress.
Note that one of the differences between Source-Detect and Backup-
Source-Detect is: in the former, the backup ingress verifies the
failure of the primary ingress slowly such as in seconds; in the
latter, the backup ingress detects the failure fast such as in a few
or tens of milliseconds.
In normal operations, the source sends the traffic to the primary
ingress. It switches the traffic to the backup ingress when it
detects the failure of the primary ingress.
The backup ingress does not import any traffic from the source into
the backup LSP in normal operations. When it detects the failure of
the primary ingress, it imports the traffic from the source into the
backup LSP to the next hops of the primary ingress, where the traffic
is merged into the primary LSP.
The source-detect is preferred. It is simpler than the backup-
source-detect, which needs both the source and the backup ingress
detect the ingress failure quickly.
3. Backup Forwarding State
Before the primary ingress fails, the backup ingress is responsible
for creating the necessary backup LSPs. These LSPs might be multiple
bypass P2P LSPs that avoid the ingress. Alternately, the backup
ingress could choose to use a single backup P2MP LSP as a bypass or
detour to protect the primary ingress of a primary P2MP LSP.
The backup ingress may be off-path or on-path of an LSP. If a backup
ingress is not any node of the LSP, it is off-path. If a backup
ingress is a next-hop of the primary ingress of the LSP, it is on-
path. When a backup ingress for protecting the primary ingress is
configured, the backup ingress MUST not be on the LSP except for it
is the next hop of the primary ingress. If it is on-path, the
primary forwarding state associated with the primary LSP SHOULD be
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clearly separated from the backup LSP(s) state.
3.1. Forwarding State for Backup LSP
A forwarding entry for a backup LSP is created on the backup ingress
after the LSP is set up. Depending on the failure-detection mode
(e.g., source-detect), it may be used to forward received traffic or
simply be inactive (e.g., backup-source-detect) until required. In
either case, when the primary ingress fails, this entry is used to
import the traffic into the backup LSP to the next hops of the
primary ingress, where the traffic is merged into the primary LSP.
The forwarding entry for a backup LSP is a local implementation
issue. In one device, it may have an inactive flag. This inactive
forwarding entry is not used to forward any traffic normally. When
the primary ingress fails, it is changed to active, and thus the
traffic from the source is imported into the backup LSP.
4. Protocol Extensions
A new object INGRESS_PROTECTION is defined for signaling ingress
local protection. The primary ingress of a primary LSP sends the
backup ingress this object in a PATH message. In this case, the
object contains the information needed to set up ingress protection.
The information includes:
o Backup ingress IP address indicating the backup ingress,
o Traffic Descriptor describing the traffic that the primary LSP
transports, this traffic is imported into the backup LSP(s) on the
backup ingress when the primary ingress fails,
o Label and Routes indicating the first hops of the primary LSP,
each of which is paired with its label, and
o Desire options on ingress protection such as P2MP option
indicating a desire to use a backup P2MP LSP to protect the
primary ingress of a primary P2MP LSP.
The backup ingress sends the primary ingress this object in a RESV
message. In this case, the object contains the information about the
status on the ingress protection.
4.1. INGRESS_PROTECTION Object
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4.1.1. Class Number and Class Type
The Class Number for the INGRESS_PROTECTION object MUST be of the
form 0bbbbbbb to enable implementations that do not recognize the
object to reject the entire message and return an "Unknown Object
Class" error [RFC2205]. It is suggested that a Class Number value
from the Private Use range (124-127) [RFC3936] specified for the
0bbbbbbb octet be chosen for this experiment. It is also suggested
that a Class Type value of 1 be used for this object in this
experiment.
The INGRESS_PROTECTION object with the FAST_REROUTE object in a PATH
message is used to control the backup for protecting the primary
ingress of a primary LSP. The primary ingress MUST insert this
object into the PATH message to be sent to the backup ingress for
protecting the primary ingress.
4.1.2. Object Format
The INGRESS_PROTECTION object has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (bytes) | Class-Num | C-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (zero) | NUB | Flags | Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ (Subobjects) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
NUB Number of Unprotected Branches
Flags
0x01 Ingress local protection available
0x02 Ingress local protection in use
0x04 Bandwidth protection
Options
0x01 Revert to Ingress
0x02 P2MP Backup
For protecting the ingress of a P2MP LSP, if the backup ingress
doesn't have a backup LSP to each of the next hops of the primary
ingress, it SHOULD clear "Ingress local protection available" and set
NUB to the number of the next hops to which there is no backup LSP.
The flags are used to communicate status information from the backup
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ingress to the primary ingress.
o Ingress local protection available: The backup ingress MUST set
this flag after backup LSPs are up and ready for locally
protecting the primary ingress. The backup ingress sends this to
the primary ingress to indicate that the primary ingress is
locally protected.
o Ingress local protection in use: The backup ingress MUST set this
flag when it detects a failure in the primary ingress and actively
redirects the traffic into the backup LSPs. The backup ingress
records this flag and does not send any RESV message with this
flag to the primary ingress since the primary ingress is down.
o Bandwidth protection: The backup ingress MUST set this flag if the
backup LSPs guarantee to provide desired bandwidth for the
protected LSP against the primary ingress failure.
The options are used by the primary ingress to specify the desired
behavior to the backup ingress.
o Revert to Ingress: The primary ingress sets this option indicating
that the traffic for the primary LSP successfully re-signaled will
be switched back to the primary ingress from the backup ingress
when the primary ingress is restored.
o P2MP Backup: This option is set to ask for the backup ingress to
use backup P2MP LSP to protect the primary ingress.
The INGRESS_PROTECTION object may contain some subobjects of
following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |Reserved (zero)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Contents/Body of subobject |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where Type is the type of a subobject, Length is the total size of
the subobject in bytes, including Type, Length and Contents fields.
4.1.3. Subobject: Backup Ingress IPv4 Address
When the primary ingress of a protected LSP sends a PATH message with
an INGRESS_PROTECTION object to the backup ingress, the object MUST
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have a Backup Ingress IPv4 Address subobject containing an IPv4
address belonging to the backup ingress if IPv4 is used. The Type of
the subobject is 1, and the body of the subobject is given below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Backup ingress IPv4 address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Backup ingress IPv4 address: An IPv4 host address of backup ingress
4.1.4. Subobject: Backup Ingress IPv6 Address
When the primary ingress of a protected LSP sends a PATH message with
an INGRESS_PROTECTION object to the backup ingress, the object MUST
have a Backup Ingress IPv6 Address subobject containing an IPv6
address belonging to the backup ingress if IPv6 is used. The Type of
the subobject is 2, the body of the subobject is given below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Backup ingress IPv6 address (16 bytes) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Backup ingress IPv6 address: An IPv6 host address of backup ingress
4.1.5. Subobject: Ingress IPv4 Address
The INGRESS_PROTECTION object may have an Ingress IPv4 Address
subobject containing an IPv4 address belonging to the primary ingress
if IPv4 is used. The Type of the subobject is 3. The subobject has
the following body:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress IPv4 address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Ingress IPv4 address: An IPv4 host address of ingress
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4.1.6. Subobject: Ingress IPv6 Address
The INGRESS_PROTECTION object may have an Ingress IPv6 Address
subobject containing an IPv6 address belonging to the primary ingress
if IPv6 is used. The Type of the subobject is 4. The subobject has
the following body:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ingress IPv6 address (16 bytes) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Ingress IPv6 address: An IPv6 host address of ingress
4.1.7. Subobject: Traffic Descriptor
The INGRESS_PROTECTION object may have a Traffic Descriptor subobject
describing the traffic to be mapped to the backup LSP on the backup
ingress for locally protecting the primary ingress. The subobject
types for Interface, IPv4 Prefix, IPv6 Prefix and Application
Identifier are 5, 6, 7 and 8 respectively. The subobject has the
following body:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Element 1 |
~ ~
| Traffic Element n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Traffic Descriptor subobject may contain multiple Traffic
Elements of same type as follows:
o Interface Traffic: Each of the Traffic Elements is a 32 bit index
of an interface, from which the traffic is imported into the
backup LSP.
o IPv4 Prefix Traffic: Each of the Traffic Elements is an IPv4
prefix, containing an 8-bit prefix length followed by an IPv4
address prefix, whose length, in bits, is specified by the prefix
length, padded to a byte boundary.
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o IPv6 Prefix Traffic: Each of the Traffic Elements is an IPv6
prefix, containing an 8-bit prefix length followed by an IPv6
address prefix, whose length, in bits, is specified by the prefix
length, padded to a byte boundary.
o Application Traffic: Each of the Traffic Elements is a 32 bit
identifier of an application, from which the traffic is imported
into the backup LSP.
4.1.8. Subobject: Label-Routes
The INGRESS_PROTECTION object in a PATH message from the primary
ingress to the backup ingress may have a Label-Routes subobject
containing the labels and routes that the next hops of the ingress
use. The Type of the subobject is 9. The subobject has the
following body:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Subobjects ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Subobjects in the Label-Routes are copied from those in the
RECORD_ROUTE objects in the RESV messages that the primary ingress
receives from its next hops for the primary LSP. They MUST contain
the first hops of the LSP, each of which is paired with its label.
5. Behavior of Ingress Protection
5.1. Overview
There are two different proposed signaling approaches to transfer the
information for ingress protection. They both use the same new
INGRESS_PROTECTION object. The object is sent in both PATH and RESV
messages.
5.1.1. Relay-Message Method
The primary ingress relays the information for ingress protection of
an LSP to the backup ingress via PATH messages. Once the LSP is
created, the ingress of the LSP sends the backup ingress a PATH
message with an INGRESS_PROTECTION object with Label-Routes
subobject, which is populated with the next-hops and labels. This
provides sufficient information for the backup ingress to create the
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appropriate forwarding state and backup LSP(s).
The ingress also sends the backup ingress all the other PATH messages
for the LSP with an empty INGRESS_PROTECTION object. An
INGRESS_PROTECTION object without any Traffic-Descriptor subobject is
called an empty INGRESS_PROTECTION object. Thus, the backup ingress
has access to all the PATH messages needed for modification to
refresh control-plane state after a failure.
The empty INGRESS_PROTECTION object is for efficient processing of
ingress protection for a P2MP LSP. For a P2MP LSP, its primary
ingress may have more than one PATH messages, each of which is sent
to a next hop along a branch of the P2MP LSP. The PATH message along
a branch will be selected and sent to the backup ingress with an
INGRESS_PROTECTION object containing the Traffic-Descriptor
subobject; all the PATH messages along the other branches will be
sent to the backup ingress containing an INGRESS_PROTECTION object
without any Traffic-Descriptor subobject (empty INGRESS_PROTECTION
object). For a P2MP LSP, the backup ingress only needs one Traffic-
Descriptor.
5.1.2. Proxy-Ingress Method
Conceptually, a proxy ingress is created that starts the RSVP
signaling. The explicit path of the LSP goes from the proxy ingress
to the backup ingress and then to the real ingress. The behavior and
signaling for the proxy ingress is done by the real ingress; the use
of a proxy ingress address avoids problems with loop detection. Note
that the proxy ingress MUST reside within the same router as the real
ingress.
[ traffic source ] *** Primary LSP
$ $ --- Backup LSP
$ $ $$ Link
$ $
[ proxy ingress ] [ backup ]
[ & ingress ] |
* |
*****[ MP ]----|
Figure 2: Example Protected LSP with Proxy Ingress Node
The backup ingress MUST know the merge points or next-hops and their
associated labels. This is accomplished by having the RSVP PATH and
RESV messages go through the backup ingress, although the forwarding
path need not go through the backup ingress. If the backup ingress
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fails, the ingress simply removes the INGRESS_PROTECTION object and
forwards the PATH messages to the LSP's next-hop(s). If the ingress
has its LSP configured for ingress protection, then the ingress can
add the backup ingress and itself to the ERO and start forwarding the
PATH messages to the backup ingress.
Slightly different behavior can apply for the on-path and off-path
cases. In the on-path case, the backup ingress is a next hop node
after the ingress for the LSP. In the off-path, the backup ingress
is not any next-hop node after the ingress for all associated sub-
LSPs.
The key advantage of this approach is that it minimizes the special
handling code required. Because the backup ingress is on the
signaling path, it can receive various notifications. It easily has
access to all the PATH messages needed for modification to be sent to
refresh control-plane state after a failure.
5.2. Ingress Behavior
The primary ingress MUST be configured with a couple of pieces of
information for ingress protection.
o Backup Ingress Address: The primary ingress MUST know the IP
address of the backup ingress it wants to be used before it can
use the INGRESS_PROTECTION object.
o Proxy-Ingress-Id (only needed for Proxy-Ingress Method): The
Proxy-Ingress-Id is only used in the Record Route Object for
recording the proxy-ingress. If no proxy-ingress-id is specified,
then a local interface address that will not otherwise be included
in the Record Route Object can be used. A similar technique is
used in [RFC4090 Sec 6.1.1].
o Application Traffic Identifier: The primary ingress and backup
ingress MUST both know what application traffic should be directed
into the LSP. If a list of prefixes in the Traffic Descriptor
subobject will not suffice, then a commonly understood Application
Traffic Identifier can be sent between the primary ingress and
backup ingress. The exact meaning of the identifier should be
configured similarly at both the primary ingress and backup
ingress. The Application Traffic Identifier is understood within
the unique context of the primary ingress and backup ingress.
o A connection between backup ingress and primary ingress: If there
is not any direct link between the primary ingress and the backup
ingress, a tunnel MUST be configured between them.
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With this additional information, the primary ingress can create and
signal the necessary RSVP extensions to support ingress protection.
5.2.1. Relay-Message Method
To protect the primary ingress of an LSP, the primary ingress MUST do
the following after the LSP is up.
1. Select a PATH message P0 for the LSP.
2. If the backup ingress is off-path (the backup ingress is not the
next hop of the primary ingress for P0), then send it a PATH
message P0' with the content from P0 and an INGRESS_PROTECTION
object; else (the backup ingress is a next hop, i.e., on-path
case) add an INGRESS_PROTECTION object into the existing PATH
message to the backup ingress (i.e., the next hop). The object
contains the Traffic-Descriptor subobject, the Backup Ingress
Address subobject and the Label-Routes subobject. The options is
set to indicate whether a Backup P2MP LSP is desired. The Label-
Routes subobject contains the next-hops of the primary ingress
and their labels. Note that for on-path case, there is an
existing PATH message to the backup ingress (i.e., the next hop),
and we just add an INGRESS_PROTECTION object into the existing
PATH message to be sent to the backup ingress. We do not send a
separate PATH message to the backup ingress for this existing
PATH message.
3. For each Pi of the other PATH messages for the LSP, send the
backup ingress a PATH message Pi' with the content copied from Pi
and an empty INGRESS_PROTECTION object.
For every PATH message Pj' (i.e., P0'/Pi') to be sent to the backup
ingress, it has the same SESSION as Pj (i.e., P0/Pi). If the backup
ingress is off-path, the primary ingress updates Pj' according to the
backup ingress as its next hop before sending it. It adds the backup
ingress to the beginning of the ERO, and sets RSVP_HOP based on the
interface to the backup ingress. The primary ingress MUST NOT set up
any forwarding state to the backup ingress if the backup ingress is
off-path.
5.2.2. Proxy-Ingress Method
The primary ingress is responsible for starting the RSVP signaling
for the proxy-ingress node. To do this, the following MUST be done
for the RSVP PATH message.
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1. Compute the EROs for the LSP as normal for the ingress.
2. If the selected backup ingress node is not the first node on the
path (for all sub-LSPs), then insert at the beginning of the ERO
first the backup ingress node and then the ingress node.
3. In the PATH RRO, instead of recording the ingress node's address,
replace it with the Proxy-Ingress-Id.
4. Leave the HOP object populated as usual with information for the
ingress-node.
5. Add the INGRESS_PROTECTION object to the PATH message. Include
the Backup Ingress Address (IPv4 or IPv6) subobject and the
Traffic-Descriptor subobject. Set or clear the options
indicating that a Backup P2MP LSP is desired.
6. Optionally, add the FAST-REROUTE object [RFC4090] to the Path
message. Indicate whether one-to-one backup is desired.
Indicate whether facility backup is desired.
7. The RSVP PATH message is sent to the backup node as normal.
If the ingress detects that it can't communicate with the backup
ingress, then the ingress SHOULD instead send the PATH message to the
next-hop indicated in the ERO computed in step 1. Once the ingress
detects that it can communicate with the backup ingress, the ingress
SHOULD follow the steps 1-7 to obtain ingress failure protection.
When the ingress node receives an RSVP PATH message with an
INGRESS_PROTECTION object and the object specifies that node as the
ingress node and the PHOP as the backup ingress node, the ingress
node SHOULD remove the INGRESS_PROTECTION object from the PATH
message before sending it out. Additionally, the ingress node MUST
store that it will install ingress forwarding state for the LSP
rather than midpoint forwarding.
When an RSVP RESV message is received by the ingress, it uses the
NHOP to determine whether the message is received from the backup
ingress or from a different node. The stored associated PATH message
contains an INGRESS_PROTECTION object that identifies the backup
ingress node. If the RESV message is not from the backup node, then
ingress forwarding state SHOULD be set up, and the INGRESS_PROTECTION
object MUST be added to the RESV before it is sent to the NHOP, which
SHOULD be the backup node. If the RESV message is from the backup
node, then the LSP SHOULD be considered available for use.
If the backup ingress node is on the forwarding path, then a RESV is
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received with an INGRESS_PROTECTION object and an NHOP that matches
the backup ingress. In this case, the ingress node's address will
not appear after the backup ingress in the RRO. The ingress node
SHOULD set up ingress forwarding state, just as is done if the LSP
weren't ingress-node protected.
5.3. Backup Ingress Behavior
An LER determines that the ingress local protection is requested for
an LSP if the INGRESS_PROTECTION object is included in the PATH
message it receives for the LSP. The LER can further determine that
it is the backup ingress if one of its addresses is in the Backup
Ingress Address subobject of the INGRESS_PROTECTION object. The LER
as the backup ingress will assume full responsibility of the ingress
after the primary ingress fails. In addition, the LER determines
that it is off-path if it is not any node of the LSP. The LER
determines whether it uses Relay-Message Method or Proxy-Ingress
Method according to configurations.
5.3.1. Backup Ingress Behavior in Off-path Case
The backup ingress considers itself as a PLR and the primary ingress
as its next hop and provides a local protection for the primary
ingress. It behaves very similarly to a PLR providing fast-reroute
where the primary ingress is considered as the failure-point to
protect. Where not otherwise specified, the behavior given in
[RFC4090] for a PLR applies.
The backup ingress MUST follow the control-options specified in the
INGRESS_PROTECTION object and the flags and specifications in the
FAST-REROUTE object. This applies to providing a P2MP backup if the
"P2MP backup" is set, a one-to-one backup if "one-to-one desired" is
set, facility backup if the "facility backup desired" is set, and
backup paths that support the desired bandwidth, and administrative
groups that are requested.
If multiple non empty INGRESS_PROTECTION objects have been received
via multiple PATH messages for the same LSP, then the most recent one
MUST be the one used.
The backup ingress creates the appropriate forwarding state for the
backup LSP tunnel(s) to the merge point(s).
When the backup ingress sends a RESV message to the primary ingress,
it MUST add an INGRESS_PROTECTION object into the message. It MUST
set or clear the flags in the object to report "Ingress local
protection available", "Ingress local protection in use", and
"bandwidth protection".
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If the backup ingress doesn't have a backup LSP tunnel to each of the
merge points, it SHOULD clear "Ingress local protection available"
and set NUB to the number of the merge points to which there is no
backup LSP.
When the primary ingress fails, the backup ingress redirects the
traffic from a source into the backup P2P LSPs or the backup P2MP LSP
transmitting the traffic to the next hops of the primary ingress,
where the traffic is merged into the protected LSP.
In this case, the backup ingress MUST keep the PATH message with the
INGRESS_PROTECTION object received from the primary ingress and the
RESV message with the INGRESS_PROTECTION object to be sent to the
primary ingress. The backup ingress MUST set the "local protection
in use" flag in the RESV message, indicating that the backup ingress
is actively redirecting the traffic into the backup P2P LSPs or the
backup P2MP LSP for locally protecting the primary ingress failure.
Note that the RESV message with this piece of information will not be
sent to the primary ingress because the primary ingress has failed.
If the backup ingress has not received any PATH message from the
primary ingress for an extended period of time (e.g., a cleanup
timeout interval) and a confirmed primary ingress failure did not
occur, then the standard RSVP soft-state removal SHOULD occur. The
backup ingress SHALL remove the state for the PATH message from the
primary ingress, and tear down the one-to-one backup LSPs for
protecting the primary ingress if one-to-one backup is used or unbind
the facility backup LSPs if facility backup is used.
When the backup ingress receives a PATH message from the primary
ingress for locally protecting the primary ingress of a protected
LSP, it MUST check to see if any critical information has been
changed. If the next hops of the primary ingress are changed, the
backup ingress SHALL update its backup LSP(s) accordingly.
5.3.1.1. Relay-Message Method
When the backup ingress receives a PATH message with an non empty
INGRESS_PROTECTION object, it examines the object to learn what
traffic associated with the LSP. It determines the next-hops to be
merged to by examining the Label-Routes subobject in the object.
The backup ingress MUST store the PATH message received from the
primary ingress, but NOT forward it.
The backup ingress responds with a RESV message to the PATH message
received from the primary ingress. If the backup ingress is off-
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path, the LABEL object in the RESV message contains IMPLICIT-NULL.
If the INGRESS_PROTECTION object is not "empty", the backup ingress
SHALL send the RESV message with the state indicating protection is
available after the backup LSP(s) are successfully established.
5.3.1.2. Proxy-Ingress Method
The backup ingress determines the next-hops to be merged to by
collecting the set of the pair of (IPv4/IPv6 subobject, Label
subobject) from the Record Route Object of each RESV that are closest
to the top and not the Ingress router; this should be the second to
the top pair. If a Label-Routes subobject is included in the
INGRESS_PROTECTION object, the included IPv4/IPv6 subobjects are used
to filter the set down to the specific next-hops where protection is
desired. A RESV message MUST have been received before the Backup
Ingress can create or select the appropriate backup LSP.
When the backup ingress receives a PATH message with the
INGRESS_PROTECTION object, the backup ingress examines the object to
learn what traffic associated with the LSP. The backup ingress
forwards the PATH message to the ingress node with the normal RSVP
changes.
When the backup ingress receives a RESV message with the
INGRESS_PROTECTION object, the backup ingress records an IMPLICIT-
NULL label in the RRO. Then the backup ingress forwards the RESV
message to the ingress node, which is acting for the proxy ingress.
5.3.2. Backup Ingress Behavior in On-path Case
An LER as the backup ingress determines that it is on-path if one of
its addresses is a next hop of the primary ingress (and for Proxy-
Ingress Method the primary ingress is not its next hop via checking
the PATH message with the INGRESS_PROTECTION object received from the
primary ingress). The LER on-path MUST send the corresponding PATH
messages without any INGRESS_PROTECTION object to its next hops. It
creates a number of backup P2P LSPs or a backup P2MP LSP from itself
to the other next hops (i.e., the next hops other than the backup
ingress) of the primary ingress. The other next hops are from the
Label-Routes subobject.
It also creates a forwarding entry, which sends/multicasts the
traffic from the source to the next hops of the backup ingress along
the protected LSP when the primary ingress fails. The traffic is
described by the Traffic-Descriptor.
After the forwarding entry is created, all the backup P2P LSPs or the
backup P2MP LSP is up and associated with the protected LSP, the
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backup ingress MUST send the primary ingress the RESV message with
the INGRESS_PROTECTION object containing the state of the local
protection such as "local protection available" flag set to one,
which indicates that the primary ingress is locally protected.
When the primary ingress fails, the backup ingress sends/multicasts
the traffic from the source to its next hops along the protected LSP
and imports the traffic into each of the backup P2P LSPs or the
backup P2MP LSP transmitting the traffic to the other next hops of
the primary ingress, where the traffic is merged into protected LSP.
During the local repair, the backup ingress MUST continue to send the
PATH messages to its next hops as before, keep the PATH message with
the INGRESS_PROTECTION object received from the primary ingress and
the RESV message with the INGRESS_PROTECTION object to be sent to the
primary ingress. It MUST set the "local protection in use" flag in
the RESV message.
5.3.3. Failure Detection and Refresh PATH Messages
As described in [RFC4090], it is necessary to refresh the PATH
messages via the backup LSP(s). The Backup Ingress MUST wait to
refresh the PATH messages until it can accurately detect that the
ingress node has failed. An example of such an accurate detection
would be that the IGP has no bi-directional links to the ingress node
or a BFD session to the primary ingress' loopback address has failed
and stayed failed after the network has reconverged.
As described in [RFC4090 Section 6.4.3], the backup ingress, acting
as PLR, MUST modify and send any saved PATH messages associated with
the primary LSP to the corresponding next hops through backup LSP(s).
Any PATH message sent will not contain any INGRESS_PROTECTION object.
The RSVP_HOP object in the message contains an IP source address
belonging to the backup ingress. The sender template object has the
backup ingress address as its tunnel sender address.
5.4. Revertive Behavior
Upon a failure event in the (primary) ingress of a protected LSP, the
protected LSP is locally repaired by the backup ingress. There are a
couple of basic strategies for restoring the LSP to a full working
path.
- Revert to Primary Ingress: When the primary ingress is restored,
it re-signals each of the LSPs that start from the primary
ingress. The traffic for every LSP successfully re-signaled is
switched back to the primary ingress from the backup ingress.
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- Global Repair by Backup Ingress: After determining that the
primary ingress of an LSP has failed, the backup ingress computes
a new optimal path, signals a new LSP along the new path, and
switches the traffic to the new LSP.
5.4.1. Revert to Primary Ingress
If "Revert to Primary Ingress" is desired for a protected LSP, the
(primary) ingress of the LSP SHOULD re-signal the LSP that starts
from the primary ingress after the primary ingress restores. After
the LSP is re-signaled successfully, the traffic SHOULD be switched
back to the primary ingress from the backup ingress on the source
node and redirected into the LSP starting from the primary ingress.
The primary ingress can specify the "Revert to Ingress" control-
option in the INGRESS_PROTECTION object in the PATH messages to the
backup ingress. After receiving the "Revert to Ingress" control-
option, the backup ingress MUST stop sending/refreshing PATH messages
for the protected LSP.
5.4.2. Global Repair by Backup Ingress
When the backup ingress has determined that the primary ingress of
the protected LSP has failed (e.g., via the IGP), it can compute a
new path and signal a new LSP along the new path so that it no longer
relies upon local repair. To do this, the backup ingress MUST use
the same tunnel sender address in the Sender Template Object and
allocate a LSP ID different from the one of the old LSP as the LSP-ID
of the new LSP. This allows the new LSP to share resources with the
old LSP. Alternately, the Backup Ingress can create a new LSP with
no bandwidth reservation that duplicates the path(s) of the protected
LSP, move traffic to the new LSP, delete the protected LSP, and then
resignal the new LSP with bandwidth.
6. Security Considerations
In principle this document does not introduce new security issues.
The security considerations pertaining to RFC 4090, RFC 4875, RFC
2205 and RFC 3209 remain relevant.
7. Compatibility
This extension reuses and extends semantics and procedures defined in
RFC 2205, RFC 3209, RFC 4090 and RFC 4875 to support ingress
protection. The new object defined to indicate ingress protection
has a class number of the form 0bbbbbbb. Per RFC 2205, a node not
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supporting this extension will not recognize the new class number and
should respond with an "Unknown Object Class" error. The error
message will propagate to the ingress, which can then take action to
avoid the incompatible node as a backup ingress or may simply
terminate the session.
8. IANA Considerations
This document does not request any IANA actions.
9. Co-authors and Contributors
1. Co-authors
Autumn Liu
Ciena
USA
Email: hliu@ciena.com
Zhenbin Li
Huawei Technologies
Email: zhenbin.li@huawei.com
Yimin Shen
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: yshen@juniper.net
Tarek Saad
Cisco Systems
Email: tsaad@cisco.com
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Fengman Xu
Verizon
2400 N. Glenville Dr
Richardson, TX 75082
USA
Email: fengman.xu@verizon.com
2. Contributors
Ning So
Tata Communications
2613 Fairbourne Cir.
Plano, TX 75082
USA
Email: ningso01@gmail.com
Mehmet Toy
Verizon
USA
Email: mehmet.toy@verizon.com
Lei Liu
USA
Email: liulei.kddi@gmail.com
Renwei Li
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: renwei.li@huawei.com
Quintin Zhao
Huawei Technologies
Boston, MA
USA
Email: quintin.zhao@huawei.com
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Boris Zhang
Telus Communications
200 Consilium Pl Floor 15
Toronto, ON M1H 3J3
Canada
Email: Boris.Zhang@telus.com
Markus Jork
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: mjork@juniper.net
10. Acknowledgement
The authors would like to thank Nobo Akiya, Rahul Aggarwal, Eric
Osborne, Ross Callon, Loa Andersson, Daniel King, Michael Yue, Alia
Atlas, Olufemi Komolafe, Rob Rennison, Neil Harrison, Kannan Sampath,
Gregory Mirsky, and Ronhazli Adam for their valuable comments and
suggestions on this draft.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, DOI 10.17487/
RFC3031, January 2001,
.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
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DOI 10.17487/RFC4090, May 2005,
.
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
DOI 10.17487/RFC4875, May 2007,
.
11.2. Informative References
[RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher,
N., and A. Fulignoli, Ed., "MPLS Transport Profile
(MPLS-TP) Linear Protection", RFC 6378, DOI 10.17487/
RFC6378, October 2011,
.
Authors' Addresses
Huaimo Chen (editor)
Huawei Technologies
Boston, MA
USA
Email: huaimo.chen@huawei.com
Raveendra Torvi (editor)
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: rtorvi@juniper.net
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